How to get back own house from joint property

Dear All, Good Day, I am Shahab (Religion: Muslim) from Tamil Nadu. I have a sister (widow). My sister husband was died more than 22 years before. she have two children 1 daughter (30 age)and 1 son (24 age). My sister’s husband was bought a land and registered the land in his name and his brother name. Then after few years he started to construct the house. But that time he has accident with a government bus and he died. At the time the house was completed first floor (pending for plastering to completion). After he died his brother was completed the ground floor (1 house attached two shop). And he is using more than 20 years and he is getting rent from the shop also. We are trying to get the share from property .But he is not given proper response to my sister. The property is still in both names (my Brother in law and his brother name). She is very poor. Because, she did not get his husband property. All of her husband properties are using from his Father-in-law (husbands father) and her husband brother. Could please you advice me to help her to getting his husband property. Regards, Shahab